The genes dumpy (dp), clot(cl) and apterous(ap) are limited on chromosomes 2 of

Question

The genes dumpy (dp), clot(cl) and apterous(ap) are limited on chromosomes 2 of Drosophila. In a series of two-point mapping crosses, the following genetic map units (mu ) were determined What is the sequence or order of the gene? Label the gene segments with the correct map distances. If a total of 100 flies were used to determined the map distances, how many of the flies would have represented recombination between the genes? A female Drosophila was isolated and shows to be heterozygous for autosomally linked genes b (black body), d (decks tarries or short legs) and c (curve wings). These genes are in the order d-b-c, with b being closer to d than to c. Show below is the genotypic arrangement for the heterozygous female fly: Give the genotypes of the gametes that represent non-chromosomes (NCO) Give the genotype of the gametes that represent single crossovers (SCO) Give the genotype of the gametes that represent double crossovers (DCO) Which of the genotype or offsprings phentotype would have the lowest frequency of occurrence?

Explanation / Answer

1. a = Correct map sequence is dp - cl - ap. This is because distance between two pair of genes is equal to the third. Like this-

b = dp --------3-------------cl ----------39----------ap

<---------------------42---------------------------->

c = Recombination between cl and ap = 39% of 1000 = 390 flies.

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